The present invention relates to photonics chips and, more specifically, to structures for grating couplers and methods of fabricating a structure including grating couplers.
Photonic chips are used in many applications and systems including, but not limited to, data communication systems and data computation systems. A photonic chip integrates optical components, such as waveguides, and electronic components, such as field-effect transistors, into a unified platform. Layout area, cost, and operational overhead, among other factors, may be reduced by integrating both types of components on a single photonics chip.
Grating couplers are commonly used to couple light from an optical fiber into an on-chip waveguide, which is considerably smaller than the optical fiber. Light that diffracts from the grating coupler will constructively interfere at a given scattering angle that is directed toward the optical fiber and into a waveguide on the photonics chip. The scattering angle of the grating coupler may be determined by the period of its constituent grooves. Grating couplers composed of silicon nitride or polycrystalline silicon may have a low coupling efficiency that limit their effectiveness for use in coupling optical signals into and out of waveguides composed of silicon nitride or polycrystalline silicon.
Improved structures for grating couplers and methods of fabricating a structure including grating couplers are needed.